Carl Moretti, the vice president of promoter Top Rank, said he received a phone call, alerting him to Chavez's positive test, from Nevada commission executive officer Keith Kizer.

The result could have steep consequences for Chavez Jr., who surrendered his World Boxing Council middleweight belt with a unanimous decision loss Saturday to Sergio Martinez that came despite a dramatic 12th-round rally by Chavez Jr.

It was the second positive test for Chavez Jr. in Nevada. After his November 2009 victory over Troy Rowland in Nevada, Chavez Jr. tested positive for a diuretic he used to shed weight.

"A subsequent positive finding could result in an enhanced punishment" in Nevada beyond the seven-month competition ban Chavez Jr. received the first time, Kizer said. "The commission will hear all the facts."

Kizer said he's awaiting pre-fight tests for all fighters for steroids, diuretics and masking agents.

"It's disappointing, past history or not," said Moretti, who added that Chavez Jr. (46-1-1, 32 knockouts) was later informed of the marijuana result by another Top Rank official.

Top Rank Chairman Bob Arum said he is braced to argue for the Nevada commission to treat his fighter with leniency because he doesn't view marijuana as a performance-enhancing drug.

"You certainly worry about the repercussions, but we have a great commission in Nevada that understands what the social issues are," Arum said. "As far as I'm concerned, marijuana should be legal and you can quote me on that."

Arum said he's been told Chavez Jr. smoked marijuana "three weeks to a month out of breaking camp because he was having trouble sleeping … it was therapeutic use for insomnia."

Medical evidence in prior Nevada commission hearings has shown marijuana would be inhaled into the system within seven days of a test to rise to the level of a positive result.

Attempts to reach Chavez Jr. on Wednesday were not immediately successful.

Chavez Jr. came under fire from his trainer Freddie Roach for giving a lethargic effort in training camp, often missing sparring sessions and spending too much time in the Las Vegas home he stayed in after previously making Roach's Wild Card Boxing Club in Hollywood his training base.

Roach said Monday that if Chavez Jr. misses one more training session next camp, the trainer will quit.

Promoters for Chavez Jr. and Martinez discussed a possible early spring rematch after Chavez Jr.'s inspiring rally from a sluggish start Saturday, when he knocked down Martinez and nearly claimed a stunning victory.

Arum railed at the idea his fighter faces such serious discipline for marijuana.

"I'm making a moral judgment," he said. "It's legal in California … it has therapeutic effects. I'm not going to step back on this one: I don't think there's anything wrong with marijuana, and if I had a vote, I'd vote to legalize it. Let's not be sanctimonious here."